Chapter 1 Introduction to System

Administration

CSNB113 SYSTEM ADMINISTRATION

College of Information Technology

Universiti Tenaga Nasional (UNITEN)

SN 2017

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Define the system administrator’s position

Log in to root

Understand the usage of su command

Know the administrator’s roles and privileges

Able to explain the skills required to be a system administrator

Discover the UNIX architecture that includes the kernel and shell

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Objectives

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A single-trusted person that is responsible to administrate the whole system

Known as superuser or root user (UNIX environment) - hold absolute power to the system

Use special user-id to log on to the system: root

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Definition of System Administrator

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Default user ID for system administrator – user ID and password is automatically created during installation

User ID = 0 (zero)

Use to perform administrative task

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root

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root (cont.)

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login: root

password:

# pwd

/

#

Command for print working directory

Output: / means root directory

Prompt: # indicates login as root

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su command - Switch from nonprivileged account to the superuser account

Other command: sudo <command>

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su

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su command with ‘-’ argument

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Argument ‘-’ ensures that

the administrator is presented the same environment as he/she logged in to root

Recreates user’s environment

Runs as separate sub shell

login: surizal

password:

$ whoami

surizal

$ su –

password:

# pwd

/root

#

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su command without ‘-’ argument

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To execute command as root but retain user’s current environment

login: surizal

password:

$ whoami

surizal

$ su

password:

# pwd

/home/surizal

#

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Exit su mode

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Exit sub shell

Press [Ctrl+d] or exit command

$ su –

password:

# exit

$

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Modify the contents or attributes of any files – although owned by other users

Initiate or kill any process – except essential for running the system

Change any user’s password – without entering the old password

Set the system clock

Control user’s access to;

Scheduling service

Networking service

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Administrator’s Privileges

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Responsible for installing, supporting, and maintaining servers or other computer systems

Installing and configuring new hardware and software

Performing routine audits of systems and software

Performing backups and restores

Applying OS updates, patches, and configuration changes

Adding, removing, or updating user accounts information such as resetting passwords

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Administrator’s Roles

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Planning and responding to service outages and other problems that occur within the system Capacity planning

Contributing and implementing Disaster Recovery (DR) and Business Continuity (BC) plans and planning

Introducing and integrating new technologies into existing data center environments

Analyzing system logs and identifying potential issues/problems in the systems

Troubleshooting any reported problems

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Administrator’s Roles (cont.)

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Scripting; light programming, project management for systems-related projects, supervising or training computer operators

Automate common or repetitive (routine) tasks

Consultant for computer problems beyond the knowledge of technical support staff

Answering technical queries

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Administrator’s Roles (cont.)

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Problem-solving skill

On call when a computer system malfunction

Quickly and correctly diagnose the crisis and produce the best solution

Analyzing skill

Understand the behavior of software

Deploy

Troubleshoot problems

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Skills Required

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Programming skill

Understand some various types of programming languages

Scripting or automation of routine tasks

Soft-skills

Users feel warm and know that their problems will be fixed in no time

Good interaction among colleagues/team members

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Skills Required

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CATEGORIES OF SYSTEM

ADMINISTRATOR

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Categories of System Administrator

UNIX Architecture

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Monitor

User Interface tool

Software

Operating System

Printer

CPU

Hard

Drive

Hardware

User

Shell

Kernel

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Kernel

Core of the operating system (OS)

Interacts with the machine hardware- most notably memory and CPU time

Part of the operating system that loads first, and it remains in main memory

Kernel code is usually loaded into a protected area of memory to prevent it from being overwritten by programs or other parts of the operating system.

When the computer starts, it goes through some initialization (booting) function, such as checking memory.

Perform housekeeping –memory, schedule processes, prioritize 18

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Type of shell

sh

One of the original shells is Bourne shell called “sh”

Developed for Unix computers by Stephen Bourne at AT&T's Bell Labs in 1977

Offers features such as input and output redirection, shell scripting with string and integer variables, and condition testing and looping.

bash

Bourne-again Shell called bash

An upgrade for “sh” with several enhancements

Linux systems still offer the “sh” shell, but "bash“ has become the new default standard.

Ability to run “sh” shell scripts unchanged.

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Type of shell

csh and tcsh C-shell," csh, have been developed by Bill Joy at Berkeley University in 1978 using C syntax

as a model. Ken Greer took csh concepts a step forward with a new shell, tcsh, which Linux systems

now offer. Tcsh fixed problems in csh and added command completion, in which the shell makes

educated "guesses" as you type, based on your system's directory structure and files. Tcsh does not run bash scripts, as the two have substantial differences.

ksh Developed by David Korn , korn shell or ksh about the time tcsh was introduced. Compatible with sh and bash. Improves on the Bourne shell by adding floating-point arithmetic, job control, command

aliasing and command completion. AT&T held proprietary rights to ksh until 2000, when it became open source.

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Prompt

The prompt, $, which is called command prompt, is issued by the shell. While the prompt is displayed, you can type a command.

The shell reads your input after you press Enter. It determines the command you want executed by looking at the first word of your input. A word is an unbroken set of characters. Spaces and tabs separate words.

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Uptime - time that the system is running ('up'), or should be up Time since last reboot

% of time the system is up

Downtime – time when the system is not running Scheduled (planned) downtime: the administrator purposely shuts

down or reboots the system; eventually the users are informed in advance

Unscheduled (unplanned) downtime: the system fails: 'crash', no power, BSOD (Blue Screen Of Death), kernel panic

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Common Term

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Uninterruptable Power Supply (UPS)

Provides immediately 'kick-in' continuous power supply from batteries without affecting the server operation

'Intelligent' UPS communicates with machine:

Warning the operator/user that mains is gone

Shuts down the machine shortly before the batteries are exhausted

Dual Power Supplies

Each is able to power the machine on its own. When one is defunct, the other can take over immediately and completely ('Redundant‘)

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Unscheduled Downtime: Precaution

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Dual fans

When one fan stops functioning, a second fan sets in automatically and immediately

Redundant hard disks

When one hard disk fails, a replacement hard disk takes over transparently

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Unscheduled Downtime: Precaution (cont.)

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1. Das, S. (2012). Your UNIX/LINUX The Ultimate Guide: Third Edition. McGraw-Hill

2. Hahn, H. (2008). Harley Hahn's Guide to Unix and Linux. California: McGraw-Hill Higher Education

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References

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